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Research of engine pistons form point of view of thermal shocks

Sieminska B., Slawinski Z.

Journal of KONES

2010

Vol. 17, No. 1

411-420

Experimental test results of thermal shocks for heavy duty pistons of combustion engines are presented in the paper. The range and the level of thermal loads were diverse and dependent from working engine conditions as well as the temperature ranges were adapted for real conditions in which pistons of the combustion engine work. temperature measurement results on crown and skirt of a piston during an engine operating under different conditions are presented in the paper. Measured temperature differences during engine operating were greatest in areas, where appeared greatest piston temperatures. Researches of thermal shocks were realized on the special testing device. The device this is automatic, controlled a computer, makes possible the realization of the cycle of research of thermal shocks in the necessary range of the temperature. Test results showed that in following cycles of thermal shocks took place stable changes ofdimensions ofthe piston too. Mainfactors effecting on the resistance of piston materials on thermal shocks are presented in the paper, at this essential parameters influent on the resistance of materials on thermal shocks are coefficients of thermal expansion and Young's modules. In particular thermal shock resistance of the different piston alloys, dependence of dimensional thermal tensions versus the undimensional heat flux, Basic parameters of the composite material AK12 +20%Al2O3 and standard, values of heat conductivity coefficient the and temperature on the composite piston surface, values of stresses due with the temperature field in piston, values strains in the composite piston due the temperature field, the example of the influence of the number of thermal shocks on the deformation of the piston sample are presented in the paper.

A novel design of the combustion engine for improvement of the efficiency and durability

Drew J., Jankowski A., Siemińska B., Sławinski Z.

Journal of KONES

2006

Vol. 13, No. 4

453-466

For the purpose of the improvement of the efficiency of the combustion engine, the new solution which links in the advantage of the engine with the spark-ignition and the diesel engine is proposes. The creature of the solution consists in the realization the process of the combustion at the constant of the volume combustion chambers. It is realized with a piston stand during the period of combustion process. This permits on maximum pressure increasing and average indicated pressure. Advantages of this solution are self-evident. The enlargement of the efficiency is obtained, and finally - decrease of fuel consumption. Whereas at such itself average indicated pressure, the of maximum decrease of appears. This maximum pressure decrease causes decrease of mechanical loads of most essential engine parts, for which the pistons belong. The novel design of the engine is In order to reduce the thermal loads on the piston and the negative effects of thermal shocks, the novel construction based design was proposed, where during the time when the thermal loads are the most severe, the mechanical loads are isolated from the inertial loads and the inertial loads are non existent. Besides the reduction of the thermal loads additional gains in overall efficiency were obtained as the result of the combustion process with the piston stopped. That system forms the part of United States Patent No. 6,481.393 B1. Thermal shocks are reasons for high temperature gradients occurring in materials of engine components and sets, what in turn makes for high total stresses, even at lack of mechanical loads that accelerate damage of the engine components. With reference to heterogeneous elements like bimetals and from materials with covers, temperature gradients will be considerably greater and will represent what is due to different material properties. Experimental test results of thermal shocks for heavy-duty pistons of combustion engines are presented in the paper. Temperature measurement results on the crown and the skirt of the piston during the Diesel engine operating under different conditions are presented in the paper. Temperatures on the piston surface in the area of combustion chamber change in an every working cycle and these changes grow less with frequency (engine speed) increasing.