About

R.P. Kingsly Ambrose is a Professor in the Department of Agricultural & Biological Engineering at Purdue University and holds the title of University Faculty Scholar. His research focuses on applying particle technology concepts to the handling and processing of grain, food, feed, and other particulate materials. His areas of interest include powder flow, particle and powder characterization, agglomeration, dust explosion, and modeling and simulation. He is involved in advancing knowledge and techniques related to food, pharmaceutical, and biological process engineering, as well as agricultural systems, safety, and health.

Selected publications

• The design and use of an optical punch for maize kernel internal crack detection

  Biosystems Engineering · 2025-07-26

  articleCorresponding
  PublisherDOI

• Expdustnet: A Hybrid Deep Learning Model for Real-Time Prediction of Suspended Explosive Dust Particle Concentrations

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Evaluating energy evolution and damage in rice kernels under compressive loadings

  Powder Technology · 2025-09-11

  articleOpen access

  Rice processing is characterized by high energy consumption and significant product losses due to kernel mechanical damage in the form of fissuring and breakage. The dependance of grain properties on many inherent and external factors makes it difficult to predict material damage. For this reason, detailed descriptions of the mechanisms of rice kernel breakage is scarce. The aim of this study is to deepen the knowledge about the rice kernel breakage mechanism under single and repeated compressive loadings, as affected by moisture content and grain size. Based on the experimental results, the mechanism of kernel weakening as the evolution of damage and the strain energy were identified. For damage evolution, a power function was proposed to describe the change in damage with the number of loading cycles. It was found that the rice kernel breakage behavior, especially the damage accumulation, resulting breakage probability and fatigue life, is dependent on the moisture content and kernel thickness. The presented study shows that the breakage of rice kernels can be predicted from the change in strain energy. The results from this work can be applied to improvement in rice processing and can significantly contribute to the reduction of material and energy losses. • The meridian cracks spreads as a result of tensile stresses around the contact area. • The kernel divides into multiple fragments more easily with increase in moisture content. • The ability of rice to accumulate the damage depends on the moisture content and thickness. • Thicker kernels are less resistant to loading and accumulates damage more easily. • The relation between damage and number of loading events is expressed by the power function.

  PublisherDOI

• Compressive Behavior of Bulk Corn: Effect of Moisture Content, Foreign Material, and Fungal Growth

  Journal of the ASABE · 2025-01-01

  articleSenior author

  Highlights Bulk corn kernels were compressed at different moisture contents and compressive forces. The stress relaxation behavior was well described by Peleg’s model. Moisture content, quality, and compressive force had a significant effect on the solidity and compressive strength of bulk corn. ABSTRACT. Understanding the mechanical properties of bulk corn is important in preventing agricultural confined space-related accidents such as grain bin entrapment and engulfment. Various qualities of bulk corn, including clean corn, corn with foreign materials (FM), and moldy corn samples were compressed at 42, 77, 106, and 130 N force levels. The compressive behavior of samples was measured at 13.2%, 16.2%, 18.9%, and 21.7% wet basis moisture contents. All samples were compressed at a strain rate of 1.25 mm/min, and the strain was kept constant for 200 s to determine the stress relaxation properties. In clean corn, the energy absorbed increased with moisture content, and the formation of clumps was observed at 21.7% moisture content. Solidity decreased with moisture content, resulting in high cohesion at moisture contents 18.9% and 21.7% for clean corn. In corn with FM, the energy absorbed did not follow a definite pattern with moisture content and no clump formation was observed. For moldy corn, the energy absorbed increased with force resulting in clump formation irrespective of the force level. This study provides further insights into the mechanical behavior of bulk corn under compression, such as solidity and compressive strength. An increase in the compressive strength or a decrease in the solidity of stored shelled corn in a grain bin increases compaction, cohesion, and the formation of clumps. The study also implies potential risks in grain bins when the kernels are moldy and stored at high moisture content. Keywords: Corn kernels, Entrapment, Foreign material, Grain bin, Moldy corn, Stress relaxation.

  PublisherDOI

• Hand Warmers: A Cost-Effective Solution to Accelerate Oxygen Depletion During Hermetic Storage

  Foods · 2025-02-07 · 1 citations

  articleOpen access

  Postharvest grain losses often result from insect infestations. Hermetic storage creates airtight conditions that limit insect survival. However, oxygen depletion can be slow during hermetic storage, leading to a loss of grain quality and market value. Oxygen scavengers offer a solution to accelerate oxygen depletion. This study evaluated hand warmers as a cost-effective alternative to commercial oxygen scavengers. Experiments in sealed empty 4-gallon glass jars with 10-h hand warmers depleted oxygen faster and more cost-effectively than those with 2000 cc Oxy-Sorb oxygen absorbers. One hand warmer depleted similar amounts of oxygen as two Oxy-Sorb oxygen absorbers and reached the 5% threshold for pest suppression in 48 h. A follow-up study found that oxygen levels in empty 4-gallon jars dropped faster than in grain-filled 25-kg hermetic bags, with jars containing two or three hand warmers reaching the 5% threshold in the first 6 h. Temperature remained constant regardless of the number of hand warmers. At the same time, the relative humidity rose in empty jars but stayed stable in grain-filled hermetic bags, with no effect on grain quality. Hand warmers can potentially serve as cost-effective alternatives to commercial oxygen scavengers in hermetic storage.

  PublisherDOI

• Factors Influencing Worker Safety in Grain Handling: An Advisory Panel Perspective

  Journal of Agricultural Safety and Health · 2024-01-01

  articleOpen accessSenior author

  HIGHLIGHTS: Findings confirmed that out-of-condition grain is a primary causal factor in grain entrapment and engulfment. The advisory panel confirmed that grain quality has implications for grain dust explosions. Findings highlighted a lack of in-depth knowledge expected from an expert panel, specifically on aspects of protective grain quality traits. ABSTRACT: Out-of-condition grain has been identified as a primary causal factor in grain entrapments and engulfments. The quality of grain also has implications for grain dust explosions. Limited research has examined exactly which elements of grain condition influence worker safety in grain handling. This research project aimed to establish an advisory panel to examine and provide input on how elements of grain condition relate to worker safety risks in grain handling. A purposeful sampling technique was used to obtain a sample of grain handling and storage experts to function in an advisory role for the project. A primary aim of this research was to understand the problem further, provide input on tested variables, and guide educational and dissemination efforts. As is true for qualitative methodologies, those selected as part of the targeted sample cannot be generalized to other experts in the field of grain handling. The final sample contained six industry representatives, five academic professionals, and two insurance/regulatory professionals. Participants interviewed had varied expertise with grain-based safety events. Of those interviewed, 23% of participants had personal experience, 54% had bystander or investigator experience, and 23% had training experience. Semi-structured interviews were conducted to further understand the problem, provide input on important elements in safe grain handling, and guide educational and dissemination efforts. Interviews were analyzed with a primary objective to identify elements of grain condition that play a role in the incidence of grain entrapment, grain engulfments, or grain dust explosions. NVivo 14 was used to conduct a thematic analysis, and four overall themes were identified, which included challenges to worker safety in the grain handling industry, areas where improved communication is needed, grain quality indicators that may play a role in safety incidents, and available mitigation strategies. The themes are the opinions of the advisory panel and may not reflect those of the entire grain handling industry.

  PublisherOA PDFDOI

• Design assessment of grain inverters in cross-flow grain dryer via CFD-DEM numerical simulation

  Biosystems Engineering · 2024-02-23 · 18 citations

  articleSenior author
  PublisherDOI

• Modelling Heat and Mass Transfer in High-Capacity Natural Convection Solar Dryers

  Journal of Agricultural Engineering (India) · 2024-01-17

  articleSenior author

  Predicting solar dryer performance under different environmental conditions or assessing their performance to dry different grains is challenging since repeatable full-scale tests are expensive and time consuming. In the present study, computational fluid dynamics approach was used to model the drying of maize in high-capacity dryers such as greenhouse and solar bubble dryer. The absorption of short-wave radiation and the greenhouse effect in the dryer with incident solar radiation was modelled using a dual-band spectrum. The distribution of airflow, temperature, and absolute humidity was analysed in this study to optimise the drying process of maize. Additionally, these results were also used to quantify the drying rate of both greenhouse and solar bubble dryer. The greenhouse dryer model overpredicted the dryer temperatures by an average of 0.12%, and overpredicted absolute humidity by 0.38 per cent. The average Root-Mean-Square Error (RMSE) of temperature prediction was 1.8 °C, and the average RMSE for absolute humidity was 0.0042 for the greenhouse model. On the other hand, the solar bubble dryer model underpredicted temperatures by 1.7%, and underpredicted humidity values by 0.3 per cent. The mean absolute percentage error for the temperature and absolute humidity prediction of the solar bubble dryer model was 1.69% and 0.28%, respectively. The predicted and observed spatial variation in the temperature was similar for both dryers.

  PublisherDOI

• Review of Modelling the Compaction of High Aspect Ratio AgriculturalFeedstock Materials

  Journal of Agricultural Engineering (India) · 2024-11-06

  article

  Agriculture feedstock materials have low bulk density and are difficult to handle and transport. Compaction can enhance the agricultural feedstock density and could be an effective solution for handling problems. To develop a better compaction process, mathematical modelling can help understand the compaction mechanism and can help predict the mechanical behaviour of feedstock materials. This paper presents a review on the energy consumption, applied pressure, as well as rheological models to predict their compaction behaviour and thus help improve compacts’ mechanical strength and reduce densification costs. In summary, energy requirement for densification of biomass depends primarily upon the pressure applied, holding on time and properties of the material. From the published literature, it could be found that the Cooper-Eaton and the Kawakita-Ludde models that considers particle rearrangement and deformation mechanism can fit pressure and density of feedstock materials during compaction. The parameters in the rheological models were correlated to the properties of the feedstock materials and can be used for optimization of machine and operational parameters.

  PublisherDOI

• Breakage behavior of corn kernels subjected to repeated loadings

  Powder Technology · 2024-01-05 · 29 citations

  articleOpen accessSenior author

  Studying the breakage behavior of corn kernels subjected to repeated compressive events, including at low frequency and low strain rate, are important for the development of breakage models for prediction of kernel breakage in handling and processing machines. The main purpose of this study was to identify the breakage behavior and mechanism of weakening of corn kernels under repeated loadings as affected by their moisture content and kernel thickness. Corn kernels at four moisture content levels (8.20%, 11.95%, 16.00%, 20.02%) and in four thickness ranges were subjected to repeated compressive loading between two parallel steel plates in quasi-static regime at a constant loading rate of 2 mm/min (strain rates from 4.7 × 10−3 to 1.0 × 10−2). Conducted experiments allow to observe the different grain breakage patterns, identify the crack initiation and its development, describe the weakening of kernels by changes in the total specific energy, plastic and elastic deformation energies, and the number of loading cycles to break (breakage probability) the kernels. The results indicate that the breakage models describing the damage and weakening of grains in terms of changes in the total and strain energy or changes in the stiffness can be used for understanding the effect of moisture content and thickness on breakage of corn kernels.

  PublisherDOI