Pavel Brabec

Computational Modeling of the Liquid LPG Injection into the Suction Manifold of an SI Vehicle Engine

LPG is a very first-rate alternative fuel for a vehicle SI engine. By mixture formation using the injection of the gaseous LPG into suction manifold of the naturally aspirated SI engine the engine power is reduced to the original petrol engine power. This advantage is corrected by mixture formation using the liquid LPG injection into the intake air to the suction manifold. The paper deals with the computational modelling of the process on the liquid LPG injection, especially of the history LPG pressure and the LPG temperature before outlet nozzle. The calibration of the computational model has been performed by the experiment. The paper proposes the design precaution on the icing of the outside on the outlet nozzle.

Vehicle SI Engine with MPI of Liquid State LPG

Abstract The first part of the article reviews the possible methods for LPG and air mixture forming (injection of gaseous or liquid state LPG) and their influence on the operating properties of an SI engine. The next chapter explains the processes that take place when liquid state LPG is injected into the air flow of an internal combustion engine intake manifold. A simplified calculation is used to show that the injection of liquid state LPG is associated with extreme low temperature of the LPG injected into intake manifold and with ice formation on the outlet nozzle. The article sets out the design of an end part injector (EPI) for liquid state LPG that reduces the risk of icing of the outlet nozzle. The results of experimental research indicate very good operational properties for a vehicle SI engine with the combustion mixture formed by the injection of liquid state LPG into the engine intake manifold. The calculation results are confirmed by recording plots of LPG pressure inside the end part of injector (EPI) and the temperature on the outlet nozzle (ON) of the LPG injector. Visual inspection of injection of liquid state LPG into the intake manifold clearly supports the performed measurements. The conclusions summarize the knowledge gained from the laboratory investigation of liquid state LPG injection into an engine intake manifold.

Spark Plug with Integrated Chamber

Spark plug with integrated chamber increases the quality of ignition of homogenous mixture in the engine cylinder. Very small amount of burning mixture bursts (outflows) from chamber (so-called flame jet ignition) which heads into faster initial phase of burning. From view of cycle to cycle variations the procedure of consequent burning is more stable. Spark plug’s case with integrated chamber is exposed by higher thermal stress than classis spark plug. This fact has to be respected during design of spark plug with integrated chamber. This article shows the how configuration of the lower part of spark plug with integrated chamber can change the type of spark and how flame-jet ignition will affect parameters of burning mixture during operating cycle.

Influence of the Mean Friction Pressure on the Temperatures of the Combustion Engine

The development of a new combustion engines is connected with endeavor for escalation of the total efficiency. Escalation of the total efficiency can be: minimization of the mechanical losses in the combustion engines or minimization of the unsuitable equipment capacity of accessories. Now research and development programs of a manufacturer of the combustion engines search effectual equipment and method for this escalation of the total efficiency. The escalation of the total efficiency is important for a minimization fuel consumption and consequently for lower emissions. The paper deals with the problem of frictional losses in internal combustion engines. It is described by measuring station built and further are shown measured values for a small car. Furthermore, in the paper presented to the selected function to approximate the measured values of friction losses, depending on the temperatures of the work fluids for a concrete RPM mode.

Compression Chamber of an SI Engine with Increased Turbulence

SHRNUTÍ Pro optimalizaci spalovaciho procesu ma vyznamny vliv turbulence v hořlave směsi ve spalovacim prostoru. Zasadni vyznam ma turbulence ve spalovacim prostoru pro tvořeni směsi a jeji hořeni ve vznětovych motorech. Pozitivni efekt na průběh vyhořivani homogenni směsi ve valci motoru prokazaly konstrukčni upravy tvaru spalovaciho prostoru pro zvyšeni intenzity turbulence jak při spalovani extremně chudych směsi, tak při spalovani stechiometrickych směsi i v plynovych zažehovych motorech, jejichž vyvoj byl realizovan na Technickem univerzitě v Liberci [5]. Využiti viřeni k ovlivněni průběhu spalovani (posileni rozvoje hořeni v počatečni fazi a zkraceni celkove doby hořeni naplně valce, sniženi mezicyklove variability) a zlepšeni energetickych, vykonovych a emisnich parametrů zažehovych motorů ukazuji odborne knihy, vědecke prace i publikovane informace o současnem vyzkumu a vyvoji na vozidlovych zažehovych motorech [1, 2, 3, 4]. Članek ukazuje konstrukčni upravy hlavy valců zkušebniho zažehoveho motoru k posileni intenzity turbulence v naplni valce a vysledek vypočtoveho modelovani intenzity turbulence ve spalovacim prostoru původniho provedeni a po provedene změně. ABSTRACT Turbulence of the combustible mixtures in the combustion chamber has a significant effect on the optimizing of the combustion process. The turbulence in the combustion chamber has a significant impact on the mixture formation and burning in a diesel engine. Modification of the combustion-chamber shape proved to have a positive effect on the process of burning a homogenous mixture in the engine cylinder due to increasing of the turbulence intensity both in the combustion of extremely poor mixtures and in combustion of stoichiometric mixtures even in gas spark ignition (SI) engines, whose development was realized at the Technical University of Liberec [5]. Specialist books, scientific work and published information on contemporary vehicle SI engine R&D show the utilization of the swirl in the cylinder charge to affect the process of combustion (consolidation of the first stage of burning and shortening of the total burning time of the cylinder charge, decreasing the intercycle variability) and improvement of the energy, power and emission parameters of SI engines [1, 2, 3, 4]. The article presents design modifications to the cylinder head of the experimental SI engine aimed at increasing the swirl intensity in the cylinder charge, and the results of the computational simulation of swirl intensity in the combustion chamber for both the original and modified design.