Effects of piston surface treatments on performance and emissions of a methanol-fueled, direct injection, stratified charge engine
Abstract
The purpose of this study was to investigate the effects of thermal barrier coatings and/or surface treatments on the performance and emissions of a methanol-fueled, direct-injection, stratified-charge (DISC) engine. A Ricardo Hydra Mark III engine was used for this work and in previous experiments at Oak Ridge National Laboratory (ORNL). The primary focus of the study was to examine the effects of various piston insert surface treatments on hydrocarbon (HC) and oxides of nitrogen (NO(x)) emissions. Previous studies have shown that engines of this class have a tendency to perform poorly at low loads and have high unburned fuel emissions. A blank aluminum piston was modified to employ removable piston bowl inserts. Four different inserts were tested in the experiment: aluminum, stainless steel with a 1.27-mm (0.050-in.) air gap (to act as a thermal barrier), and two stainless steel/air-gap inserts with coatings. Two stainless steel inserts were dimensionally modified to account for the coating thickness (1.27-mm) and coated identically with partially stabilized zirconia (PSZ). One of the coated inserts then had an additional seal-coat applied. The coated inserts were otherwise identical to the stainless steel/air-gap insert (i.e., they employed the same 1.27-mm air gap). Thermal barrier coatings were employed in an attempt to increase combustion chamber surface temperatures, thereby reducing wall quenching and promoting more complete combustion of the fuel in the quench zone. The seal-coat was applied to the zirconia to reduce the surface porosity; previous research suggested that despite the possibly higher surface temperatures obtainable with a ceramic coating, the high surface area of a plasma-sprayed coating may actually allow fuel to adhere to the surface and increase the unburned fuel emissions and fuel consumption.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- July 1994
- Bibcode:
- 1994STIN...9512648W
- Keywords:
-
- Ceramic Coatings;
- Gaps;
- Injection;
- Loads (Forces);
- Pistons;
- Surface Treatment;
- Thermal Control Coatings;
- Aluminum;
- Combustion;
- Combustion Chambers;
- Fuel Consumption;
- Hydrocarbons;
- Nitrogen Oxides;
- Porosity;
- Stainless Steels;
- Surface Temperature;
- Thickness;
- Zirconium Oxides;
- Mechanical Engineering