Effects of ethanol-unleaded gasoline blends on cyclic variability and emissions in an SI engine

One important design goal for spark-ignited engines is to minimize cyclic variability. A small amount of cyclic variability (slow burns) can produce undesirable engine vibrations. On the other hand, a larger amount of cyclic variability (incomplete burns) leads to an increase in hydrocarbon consumption and emissions. This paper investigates the effects of using ethanol-unleaded gasoline blends on cyclic variability and emissions in a spark-ignited engine. Results of this study showed that using ethanol-unleaded gasoline blends as a fuel decreased the coefficient of variation in indicated mean effective pressure, and CO and HC emission concentrations, while increased CO2 concentration up to 10vol.% ethanol in fuel blend. On the other hand, after this level of blend a reverse effect was observed on the parameters aforementioned. The 10vol.% ethanol in fuel blend gave the best results. (C) 2004 Elsevier Ltd. All rights reserved

Thermal balance of a four stroke SI engine operating on hydrogen as a supplementary fuel

This paper investigates the effects of adding constant quantity hydrogen to gasoline-air mixture on SI engine thermal balance and performance. A four stroke, four-cylinder SI engine was used for conducting this study

Temperature and air-fuel ratio dependent specific heat ratio functions for lean burned and unburned mixture

The most important thermodynamic property used in heat release calculations for engines is the specific heat ratio. The functions proposed in the literature for the specific heat ratio are temperature dependent and apply at or near stoichiometric air-fuel ratios. However, the specific heat ratio is also influenced by the gas composition in the engine cylinder and especially becomes important for lean combustion engines

Posterior Epidural Migration of a Sequestered Lumbar. Intervertebral Disc Fragment

AIM: Posterior epidural migration of a sequestered lumbar intervertebral disc fragment (PEMSLIDF) is an extremely rare condition published so far only as case reports or small case series (ranging between 2 to 8 cases). Diagnosing this condition is often challenging and the diagnosis is usually made intraoperatively. The affected patients usually suffer cauda equina syndrome (CES). In the present study, we aimed to discuss the clinical and radiological findings, types and features of surgical therapies, and outcomes of 9 patients with PEMSLIDF. MATERIAL and METHODS: This study included 9 (0.36%) patients with PEMSLIDF among 2470 patients who underwent lumbar disc hernia surgery between August 2002 and September 2012. The preoperative clinical and radiological properties of the patients were evaluated. The postoperative outcomes were assessed using neurological examination, radiological imaging, visual analog scale (VAS) and modified Odom criteria. RESULTS: RESULTS: As far as we know, this study is the largest case series examining the characteristics of PEMSLIDF. Seven (77.8%) of our patients were male and 2 (22.2%) were female and they had a mean age of 49.5 years (range 28-70 years). The mean duration from symptom onset to hospital admission was 7.4 days. Seven patients had CES. All patients underwent sequestrectomy and discectomy via posterior microsurgery. The patient outcomes were evaluated by the Modified Odom criteria and the outcome was excellent in two (22.2%) patients, good in 4 (44.5%), fair in 2 (22.2%), and poor in 1 (11.1%). CONCLUSION: The entire free fragment can usually be excised via the posterior microsurgery technique. Early surgical treatment is of great importance to prevent more serious neurological deficits