Abstract
Experimental results of the four-stroke CI direct injection engine fed with vegetable fuel - methyl esters of the rapeseed oil in aspect pressure course and heat release are presented in the paper. Aim realized researches was estimation of the influence feed of the CI engine a vegetable fuel on performance of the CI engine mainly in an aspect of the heat release. This influence estimated on the basis of engine research on dynamometer test bench with additional high-frequency measurement of the pressure in the combustion chamber and the feed system and lift of nozzle needle. In estimation works there were performed: the analysis change route of increasing of the pressure in the injection pipeline of the engine feed system and as result of appointment of relative characteristics of the heat release quantity during combustion process. This analysis realized basing on average values of 100 engine work cycles received from experimental measurement on engine dynamometer test bench.
Characteristics of the relative heat release quantity during combustion process were appointed basing on the analysis of 100 engine work cycles received from experimental indicator diagrams. Indicator diagrams were obtained at work of the engine according to the external speed engine characteristics. The analysis of indicator diagrams of the engine oriented on to calculating characteristics of the heat release was realized at the regard of the change composition and the working charge quantity of kilo mole during combustion process and at neglect of losses of heat caused with the dissociation combustion products. The quantity heat exchanged between the working charge and walls combustion chamber was appointed basing on the empirical dependence for coefficient proposed by Woschni.
Average values of pressure courses of vegetable fuels in the injection's pipeline and speeds of pressure increasing in it were bigger in the all range of engine rotational speeds comparatively with a standard hydrocarbon diesel fuel: differences of these speeds were of 7.0% at the speed of the maximum torque, and 6.1% at the speed of maximum power, the maximum speed of heat release has greater value at engine feed with the vegetable fuel to with a standard hydrocarbon diesel fuel, quantity of heat transferred to combustion chamber walls at engine feed a vegetable fuel was greater in comparison to a standard hydrocarbon diesel fuel.
Test results indicate the two-phase- course of combustion process. The speed of the heat release concerning combustion of vegetable fuel is greater comparatively for this speed concerning the diesel oil. Initial values of speed jet of injected fuel, the drop break-up terms and the spray ranges were comparable for both fuels. These proprieties have an essential influence on performances of the engine.
Keywords: Powertrain technology, alternative fuel engines, rapeseed oil methyl esters, fuel injection, heat release