R.K. Mishra

Soot Formation and Its Effect in an Aero Gas Turbine Combustor

Abstract Soot formation and the effect of soot deposit on the performance and integrity on an aero gas turbine combustor has been studied. Defective atomizer or blockage of air passages creates a fuel rich mixture which promotes soot formation in combustor primary zone. The temperature field and soot concentration inside the liner has been analyzed at high equivalence ratio using computational model in CFX. The peak temperature in primary zone increases till equivalence ratio reaches ϕ=1.1. But at high equivalence ratio, i.u2009e., ϕ≥1.2, the peak temperature in primary zone decreases and that in dilution zone increases. Soot concentration increases at liner front end as well as in dilution zone when equivalence ratio increases from 1.25 to 3.0. Erosion and distortion of atomizer flow passages cause higher spray cone angle which again increases the soot concentration. Soot deposit inside liner has detrimental effect on the life and performance of the combustor as well as of the aero engine.

Effect of Spray Cone Angle on Flame Stability in an Annular Gas Turbine Combustor

Abstract Effect of fuel spray cone angle in an aerogas turbine combustor has been studied using computational fluid dynamics (CFD) and full-scale combustor testing. For CFD analysis, a 22.5° sector of an annular combustor is modeled and the governing equations are solved using the eddy dissipation combustion model in ANSYS CFX computational package. The analysis has been carried out at 125 kPa and 303 K inlet conditions for spray cone angles from 60° to 140°. The lean blowout limits are established by studying the behavior of combustion zone during transient engine operation from an initial steady-state condition. The computational study has been followed by testing the practical full-scale annular combustor in an aerothermal test facility. The experimental result is in a good agreement with the computational predictions. The lean blowout fuel–air ratio increases as the spray cone angle is decreased at constant operating pressure and temperature. At higher spray cone angle, the flame and high-temperature zone moves upstream close to atomizer face and a uniform flame is sustained over a wide region causing better flame stability.

Effect of Fuel Particle Size on the Stability of Swirl Stabilized Flame in a Gas Turbine Combustor

Abstract Combustion stability is examined in a swirl stabilized aero gas turbine combustor using computational fluid dynamics. A 22.5° sector of an annular combustor is modeled for the study. Unstructured tetrahedral meshes comprising 1.2u2009×u2009106 elements are employed in the model where the governing equations are solved using CFD flow solver CFX using eddy dissipation combustion model. The effect of fuel particle size on the combustion and its stability has been studied at steady state and transient conditions. The time for complete evaporation is increased exponentially when drop size increases. It delays heating up the mixture and subsequent ignition. This strongly affects the stability of the combustion flame as the incoming fresh mixture will have a quenching effect on the existing temperature field. Transient analysis at low fuel-air ratio and high particle size shows that there is a series of flame extinction and re-ignition prior to complete extinction which is observed from the fluctuation of gas temperature in the primary zone.

Analysis of Compressor Surge in a Military Turbojet Engine: A Case Study

Abstract A case of compressor surge with bang noise during takeoff roll is investigated and presented in this paper. Fatigue failure of compressor rotor blades during takeoff is found to disturb the aerodynamics of compressor flow causing the surge. Based on evidences, failure of rotor blades and compressor surge due to over-speed and foreign object debris is ruled out. The paper presents the methodology adopted for the investigation and also suggests remedial measures necessary to prevent such incidents.

Lean Blow-out Studies in a Swirl Stabilized Annular Gas Turbine Combustor

Abstract Lean blow out characteristics in a swirl stabilized aero gas turbine combustor have been studied using computational fluid dynamics. For CFD analysis, a 22.5° sector of an annular combustor is modeled using unstructured tetrahedral meshes comprising 1.2u2009×u2009106 elements. The governing equations are solved using the eddy dissipation combustion model in CFX. The primary combustion zone is analyzed by considering it as a well stirred reactor. The analysis has been carried out for different operating conditions of the reactants entering into the control volume. The results are treated as the base-line or reference values. Combustion lean blow-out limits are further characterized studying the behavior of combustion zone during transient engine operation. The validity of the computational study has been established by experimental study on a full-scale annular combustor in an air flow test facility that is capable of simulating different conditions at combustor inlet. The experimental result is in a good agreement with the analytical predictions. Upon increasing the combustor mass flow, the lean blow out limit increases, i.e., the blow out occurs at higher fuel-air ratios. In addition, when the operating pressure decreases, the lean blow out limit increases, i.e., blow out occurs at higher fuel-air ratios.

Failure Analysis of High-Pressure Compressor Blade in an Aero Gas Turbine Engine

Failure of high-pressure compressor rotor blade in an aero gas turbine engine is analyzed to determine its root cause. Forensic and metallurgical investigations are carried out on the blade and failed parts. The failure of the platform ladder is found to the first in the chain of events that led to the compressor blade failure. The mode of failure in the blade is found to be fatigue and has originated from the damaged region on the leading edge caused by dislodgement of platform ladder. The failure has caused extensive damages in high-pressure compressor module and also in downstream turbine blades as a secondary effect.

Laparoscopic vs Abdominal Hysterectomy in the Management of Benign Gynecological Diseases: A Tertiary Hospital Experience in Punjab

Objectives: • To compare laparoscopically assisted vaginal hysterectomy (LAVH) with total abdominal hysterectomy (TAH) in a retrospective analysis for the management of benign diseases. • To evaluate average age, hospital stay, blood loss, intraoperative and postoperative complication rates, and postoperative pain management. Study design: • A retrospective case–control study in Christian Medical College and Hospital, Ludhiana, was carried out comparing LAVH) and TAH for a period of 1 year between November 2014 and October 2015. • Sample size: A total of 124 patients (62 for LAVH and 62 for TAH). Results: • The LAVH is associated with shorter hospital stay as compared with TAH (3.3 and 5.8 days; p < 0.001), less amount of blood loss (176 and 420 mL; p < 0.022), and less number of postoperative complication rates (4.76 and 14.5%; p = 0.061). • The LAVH is also associated with less number of blood transfusions. Only 8 patients required blood transfusion intraor postoperatively following LAVH, and 25 patients for TAH. • The operation time in LAVH is slightly longer as compared with TAH (173 vs 153 minutes; p = 0.999). • Analgesic drug requirement to control pain was significantly less in LAVH. About 38.7% required continous opoid infusion pump following TAH, and only 6.35% following LAVH. Conclusion: • The LAVH is a safe and reliable alternative to open surgery in the management of benign gynecological diseases, with significantly reduced hospital stay and complications.

Laparoscopic Management of Stomach Sleeve Obstruction after Sleeve Gastrectomy

Introduction: Stomach sleeve obstruction can occur after sleeve gastrectomy (SG). It results in absolute intolerance to liquid and food intake. The obstruction of sleeve may be because of stomach torsion, twisting, kinking, folding, adhesions, and stenosis/narrowing. We present a case report of two patients with absolute intolerance to liquid intake because of sleeve obstruction. The reason for obstruction was folding, twisting, and partial torsion of the stomach sleeve after SG. Case/technique description: Two patients with absolute intolerance to liquid intake were received on day 5 and on day 12 after undergoing primary laparoscopic SG. The endoscopy findings were similar in both the cases. It was not possible to reach pylorus without great difficulty and high level of maneuverability. The laparoscopic findings were twisting and partial torsion due to laxity of the sleeve. Gastropexy was done in both the cases. The recovery in terms of excellent tolerance for liquid intake was immediate and that too without recurrence. Discussion: The distal passage for food and liquid in the lumen of the sleeve should remain very smooth. The lumen can accept arrival of the Ryle’s tube or gastric calibration tube up to antrum without any great assistance. This will not be possible in case of improper architecture of the crafted sleeve. The design of the sleeve may be improper from the beginning or it may mutate because of abnormal adhesion at any time during postoperative course. Symptoms and endoscopic findings are diagnostic of the problem. Laparoscopic correction of the architecture of the sleeve by doing adhesiolysis and gastropexy is successful.

Comparative Study of Surgical Approaches for Renal Pelvic Stones in a Northern Rural Medical College

Introduction: Retroperitoneal pyelolithotomy (RPL) can be used as an alternative to open pyelolithotomy (OP) when other modalities of stone removal fail. This procedure even has potential to replace noninvasive techniques in selective subsets of patients. Aims and objectives: The aim of this study was to study the efficacy, safety, and outcome of retroperitoneal laparoscopic pyelolithotomy. The study compared the advantages and complications of RPL and OP. Materials and methods: This study was conducted in the Department of Surgery, Maharishi Markandeshwar Institute of Medical Science and Research, Maharishi Markandeshwar University, Ambala, from January 2012 to December 2015. A total of 280 patients of solitary renal pelvic stone were selected, out of whom 160 who underwent RPL were considered in group I and 120 patients who underwent OP were considered in group II. The patients included were of age group 12 to 80 years, with unilateral and bilateral solitary renal pelvis calculus and stone size of 10 mm to 3 cm. Patients with recurrent or residual stones after pyelolithotomy, intractable urinary tract infection, and having extrarenal pelvis and any anatomical renal abnormalities were excluded from the study. Results: In this study, mean age was 37.1 and 46.66 years in groups I and II respectively. Male to female ratio was 2.33:1. Mean operative time was 75.33 ± 16.90 and 65.83 ± 12.35 minutes respectively, in groups I and II respectively (p < 0.001). Pyelotomy closure time and Double-J (DJ) stent insertion time were 5.2 minutes (with standard deviation [SD] of 4.3) and 9.8 (with SD of 3.7) respectively, in group I as compared with 4.2 minutes (with SD of 2.7) and 6.1 (with SD of 2.9) in group II. Mean hospital stay was less in group I at 3.76 ± 0.85 days and, in group II, it was 5.36 ± 1.96 days (p < 0.001). Postoperative anesthesia requirement was 2.23 ± 0.62 days (339 ± 93 mg) and 5.36 ± 0.96 days (804 ± 144 mg) in groups I and II respectively (p < 0.001). Conclusion: The RPL is a noninvasive and cost-effective method along with minimal scar mark. It has the advantages over OP of having fewer complications, less postoperative pain, better cosmesis, and less hospital stay. ORIGINAL ARTICLE 1,5,6Postgraduate Resident, 2Professor, 3Assistant Professor 4Senior Resident, 7Chief 1-6Department of Surgery, Maharishi Markandeshwer Institute of Medical Sciences and Research, Mullana, Haryana, India 7World Laparoscopy Hospital, Gurugram, Haryana, India Corresponding Author: Rikki Singal, Professor, Dr. Kundan Lal Hospital, Ahmedgarh, Punjab, India, e-mail: singalsurgery@ yahoo.com 10.5005/jp-journ ls-10033-1292

Short- and Long-term Effects of Laparoscopic Sleeve Gastrectomy on Body Weight and Glucose Homeostasis in Diabetic Patients

Introduction: Laparoscopic sleeve gastrectomy (LSG) is being performed more frequently and is currently very “trendy” among laparoscopic surgeons involved in bariatric surgery. Laparoscopic sleeve gastrectomy is associated with a marked reduction of ghrelin secretion, which is produced by the gastric fundus involved in mealtime hunger regulation, and it is also known to extend several diabetogenic effects. Aim: The aim of this study is to assess the shortand longterm effects of LSG on body weight and glucose homeostasis in morbidly obese diabetic patients. Materials and methods: This is a prospective study that was conducted on 40 diabetic patients randomly selected suffering from morbid obesity that had type II diabetes mellitus (T2DM). Patients were managed by LSG in AL-Zahraa Hospital, Faculty of Medicine for girls, Al-Azhar University, from January 2012 to December 2015, to assess the shortand long-term effects of the procedure on glucose homeostasis. Results: The study was conducted on 40 patients of morbid obesity that had T2DM. The preoperative mean fasting blood glucose (FBG) level was 209.3 ± 36.6 (156–299) mg/dL and postoperatively was 172.5 ± 29 (130–250) mg/dL, 125.6 ± 16.7 (99–169) mg/dL, 111.7 ± 20.9 (77–167) mg/dL, 105 ± 18.3 (73–137) mg/dL, and 102.9 ± 21 (70–145) mg/dL at 1 day and 3, 6, 9, and 12 months respectively. Postoperatively, the FBG levels were improved with significant declining at 1 day (p < 0.001), 3 months (p < 0.001), and 6 months (p < 0.004) but nonsignificant declining at 9 months (p < 0.25) and 12 months (p = 1). Conclusion: Laparoscopic sleeve gastrectomy is an effective surgical treatment for most severely or morbidly obese patients with DM. Weight loss is effective treatment for patients with these medical problems. The SG is associated with a high rate of resolution of T2DM at 12 months after surgery in severely obese patients with T2DM.